Effect of Pulse Frequency on the Corrosion Behavior of Microarc Oxidation Coating on Mg Alloys in SBF

Abstract:

The corrosion behavior of microarc oxidation (MAO) coatings prepared on AZ31 Mg alloys at 50, 100, 300, 500, 1000 and 3000 Hz was studied in simulated body fluid (SBF). The microstructure, porosity, and chemical phase composition of the samples before and after corrosion were analyzed. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were employed to characterize the corrosion performance. The results show that pulse frequency plays an important role on the corrosion resistance of the MAO coating. The corrosion current density decreases and electrochemical impedance increases with the increase of the pulse frequencies, which result from the dense microstructure at high frequency. The coating produced at 3000 Hz exhibits the largest corrosion resistance with the densest morphology in the present study.

Key words:magnesium alloy; microarc oxidation; pulse frequency; corrosion; simulated body fluid